* For the moment, strengthened Prime Minister Margaret Thatcher and her Conservative government by diluting the strength of the Labour opposition in Parliament.

* Pushed a small group of senior Labour moderates, including Shirley Williams and former Foreign Secretary David Owen, to the momentous decision of leaving the party and trying to set up a separate social democratic party in alliance with the Liberal Party, with former Common Market leader Roy Jenkins and perhaps with some small support from right-wing union members. Their prospects for electoral success do not seem bright, but they say they have no choice.

One lesson of the current intensive political maneuvering in Britain is this: that if moderates stay away from party meetings and fail to push their own views , extremist minorities of either left or right can take over.

In Britain, as in the United States, more and more people are restless and dissatisfied with politicians and other leaders in the center. Alarmed by industrial decline, economic recession, and worsening detente abroad, voters are moving away from the center ground.

In Britain many have turned to the right and wholeheartedly support Mrs. Thatcher and her strict approach to budget economies (despite unemployment now standing at almost 2 1/2 million people).

Many on the left have decided that moderate Labour MPs simply don't move quickly enough to realize the socialist aims regularly voted by party conference , which is 90 percent dominated by trade union officials voting their memberships in huge blocs, or "card votes."

Activists can carry the day if they work hard and take advantage of what has been an apathy of the center.

Many thoughtful people in Britain would echo the words of one right-wing union leader after the Labour Party conference vote. The Shopworkers' Union is usually moderate, but a minority of activists within the union executive managed to commit the union delegation to the Jan. 24 Wembley Conference to a course that, in fact, was worse for the moderate cause than most of the union apparrently wanted.

A sorrowful union official said after the conference: "Well, it's a warning to moderates everywhere to stand up for what they believe in. Otherwise, they'll lose. . . ."

The issue at the conference was whether Labour MPs should continue to have the sole right to choose the party's leader and deputy leader.

For decades, left-wing unionists, and the activists in the constituency labor parties (those at the grass roots who ring doorbells and lick stamps at every election), had been upset at the parliamentary leadership.

Although the unions dominated every annual conference, they could never dethrone the parliamentary leadership. But gradually changes in the party constitution, a growing gap between leaders' socialist rhetoric and their actual performance in office, the way Marxism became fashionable with young intellectuals in the 1960s, widespread disillusion with Britain's entry into the European Community, and other factors strengthened the left and weakened the center.

The party is getting much publicity from the conference and Labour Party leader Michael Foot has been weakened despite his pleas for unity and appeals to the right- wingers not to desert.

It was clear that the moderate "gang of three" were about to split off and form their own party to appeal to the center-left. On Jan. 25, the gang met with some supporters and Roy Jenkins at Dr. Owen's Limehouse home and took another step: formation of a "Council for Social Democracy" promising a "new start" in British politics.